Korean J Orthod.  2016 Jul;46(4):189-198. 10.4041/kjod.2016.46.4.189.

Stress distributions in peri-miniscrew areas from cylindrical and tapered miniscrews inserted at different angles

• Choi SH
• Kim SJ
• Lee KJ
• Sung SJ
• Chun YS
• Hwang CJ

• KMID: 2392199
• DOI: http://doi.org/10.4041/kjod.2016.46.4.189

Abstract

OBJECTIVE
The purpose of this study was to analyze stress distributions in the roots, periodontal ligaments (PDLs), and bones around cylindrical and tapered miniscrews inserted at different angles using a finite element analysis.
METHODS
We created a three-dimensional (3D) maxilla model of a dentition with extracted first premolars and used 2 types of miniscrews (tapered and cylindrical) with 1.45-mm diameters and 8-mm lengths. The miniscrews were inserted at 30°, 60°, and 90° angles with respect to the bone surface. A simulated horizontal orthodontic force of 2 N was applied to the miniscrew heads. Then, the stress distributions, magnitudes during miniscrew placement, and force applications were analyzed with a 3D finite element analysis.
RESULTS
Stresses were primarily absorbed by cortical bone. Moreover, very little stress was transmitted to the roots, PDLs, and cancellous bone. During cylindrical miniscrew insertion, the maximum von Mises stress increased as insertion angle decreased. Tapered miniscrews exhibited greater maximum von Mises stress than cylindrical miniscrews. During force application, maximum von Mises stresses increased in both groups as insertion angles decreased.
CONCLUSIONS
For both cylindrical and tapered miniscrew designs, placement as perpendicular to the bone surface as possible is recommended to reduce stress in the surrounding bone.

Keyword

Orthodontic miniscrews; Miniscrew design; Finite element analysis; Stress

MeSH Terms

Bicuspid
Dentition
Finite Element Analysis
Head
Maxilla
Periodontal Ligament

Figure

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  Figure 1 Schematic diagrams of the 1508C and 1508T miniscrews. A, Cylindrical type. B, Taper type. D1, External diameter; d, internal diameter; ℓ1, length of threaded part; ℓ2, length of tapered part.

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  Figure 2 Three miniscrew insertion angles are shown; the insertion angles were measured between the miniscrew and bone surface. A, 30°; B, 60°; C, 90°.

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  Figure 3 The von Mises stress distributions during miniscrew placement at the roots. P, Palatal view; B, buccal view; left, first molar; right, second premolar.

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  Figure 4 The von Mises stress distributions during miniscrew placement at the periodontal ligaments. P, Palatal view; B, buccal view; left, first molar; right, second premolar.

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  Figure 5 The von Mises stress distributions during miniscrew placement in cortical bone (buccal view). M, Mesial side; D, distal side.

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  Figure 6 The von Mises stress distributions during miniscrew placement in cancellous bone (buccal view). M, Mesial side; D, distal side.

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  Figure 7 The von Mises stress distributions in cortical bone during force application (buccal view). M, Mesial side; D, distal side.

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  Figure 8 The von Mises stress distributions in cancellous bone during force application (buccal view). M, Mesial side; D, distal side; A, apical side; O, occlusal side.

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